<p>A direct comparison between multicycle freeze-thawing (FT) and ice recrystallization-thawing (IT) treatments of rice starch granules was performed. Both these treatments generated grooves and shallow indentations on the granular surface as judged by Scanning Electron Microscopy. The relative crystallinity and apparent amylose content were both decreased by FT and IT treatments and these parameters were further decreased with the increased treatment repeats. Both treatments increased the swelling power and solubility. However, the same number of treatment repeats did not show significant difference between FT and IT for crystallinity, amylose content, swelling power and solubility. Rapid Visco Analysis showed an increase in peak viscosity and a decrease in breakdown, final viscosity and setback value whereas their pasting temperatures and time were indifferent for both treatments. Thermal analysis documented that FT and IT treatments had only minor effect on the gelatinization transition temperatures. Nevertheless, the enthalpy of gelatinization was significantly decreased by both modifications, and this effect decreased with repeated treatment. In summary, IT treatment can be used to modify rice starch providing the same structural and physicochemical properties as FT and can hence shorten the process time and energy demand as compared to FT treatment.</p>

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Comparison of freeze-thawing and ice recrystallization-thawing on structural and physicochemical properties of granular rice starch

  • Thewika Keeratiburana,
  • Tian Fu,
  • Achmat Sarifudin,
  • Siriwat Soontaranon,
  • Andreas Blennow

摘要

A direct comparison between multicycle freeze-thawing (FT) and ice recrystallization-thawing (IT) treatments of rice starch granules was performed. Both these treatments generated grooves and shallow indentations on the granular surface as judged by Scanning Electron Microscopy. The relative crystallinity and apparent amylose content were both decreased by FT and IT treatments and these parameters were further decreased with the increased treatment repeats. Both treatments increased the swelling power and solubility. However, the same number of treatment repeats did not show significant difference between FT and IT for crystallinity, amylose content, swelling power and solubility. Rapid Visco Analysis showed an increase in peak viscosity and a decrease in breakdown, final viscosity and setback value whereas their pasting temperatures and time were indifferent for both treatments. Thermal analysis documented that FT and IT treatments had only minor effect on the gelatinization transition temperatures. Nevertheless, the enthalpy of gelatinization was significantly decreased by both modifications, and this effect decreased with repeated treatment. In summary, IT treatment can be used to modify rice starch providing the same structural and physicochemical properties as FT and can hence shorten the process time and energy demand as compared to FT treatment.